Major Stryker Level Format

Major Stryker Level Format

File:Major Stryker Level Format.png
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Format type	Map/level
Map type	2D tile-based
Layer count	1
Tile size (pixels)	16×16
Viewport (pixels)	256×160
Games	Major Stryker

File Format

The basic layout of a level file is as follows:

Data type	Description
Char[12] cMaskTiles	filename of the masked tile graphics
Char[12] cSolidTiles	filename of the solid tile graphics
Char[12] cBackdrop	filename of the backdrop tile graphics
Char[12] cUnused1	unused filename (always "dropa.dr1")
Char[12] cUnused2	unused filename (always "attr00.dr1")
Char[12] cMusic	filename of the music file
Char[12] cUnused3	unused filename (always "mboss.dr1")
UINT16LE iFlags	Flags for lights etc (see below)
UINT16LE iWidth	Width of map, in tiles (always 32)
UINT16LE iActorSize	Number of UINT16LE values in the actor data
UINT16LE[iActorSize] iActorData	Actor entries (3 values per actor, see below)
BYTE[240] bMaskAttributes	Tile attributes (one byte per tile, see below)
BYTE[240] bTileAttributes	Tile attributes (one byte per tile, see below)
UINT16LE[16767] iTileData	Tile codes for the entire level

The bits in the iFlags value have the following meaning:

Bit mask	Effect
0x0001	none (this is ALWAYS set but has no effects at all)
0x0002	lightning (only used in E2M1)
0x0004	scroll bottom plane faster (for bosses in E1M12, E2M12, E3M12)

The tile attribute bits have the following effects:

Bit mask	Effect
0x10	road
0x20	animated (see below)
0x40	shootable
0x80	blocking (any direction)

Actor entries use the following data structure:

Data type	Description
UINT16LE iType	ID number of this actor
UINT16LE iPosX	X coordinate of this actor, in tile units
UINT16LE iPosY	Y coordinate of this actor, in tile units

The game ignores the iWidth value read from the file and sets it back to 32, thus the level's height will always be 523, leaving 31 UINT16LE values unused at the end of the tile data.

Tile animation

Animated tiles display as a loop of 4 different images, consisting of the tile in question plus the 3 tiles following it in the tileset. For example, let's say that tile index 50 has its animated flag set in the attributes array. At locations where that tile is placed, the game actually displays a sequence of indices 50, 51, 52, 53, repeated.

Tile Data

The range of valid tile data goes from 0 to 0x1ED0. Some levels also contain the invalid values 0x22C0 and 0x22E0 in the 31 unused tiles at the end, which must be handled separately.

• Values smaller than $F0 are tile indices for the masked tileset.

• Subtract $F0 from any other valid value to get an offset into the solid tileset in memory (divide the offset by 32 to get a tile index).

The map layout is special because the game uses parallax scrolling. The first 16 tiles of each row make up the actual map, the last 16 tiles of each row make up the layer that scrolls below the actual map (at half the speed). Actors can be placed in both of these "layers" (see below).

Actor IDs

Some actors spawn objects into the level, but some are actually modifiers that affect another actor in some way. Modifiers act on the actor that appears right before. In some cases, a single in-game entity can be described by up to 4 different actors in a row due to modifiers.

Formations of multiple ships are spawned via a combination of at least two actors: First, a formation type describes the number and position of ships and their movement. After that, the next actor describes the type of ships to use in the formation. This pair of actors may be followed by additional modifiers. It seems that some (all?) formations can also appear without a "ship selector", in which case they will default to a certain ship type (varies for each formation).

Actors can be "foreground" (same plane as the player) or "background" (behind the player, no collision). Which actor appears on which layer is hardcoded based on the actor ID.

Finally, it's worth noting that some actors don't have a sprite-based graphical representation, but rely on the level's tile map to have an appropriate tile at the actor's location. When these actors are destroyed, they draw a "destroyed" image on top of the map tiles.

Here's what's known so far:

Foreground actors

ID	Description
1	1x1 gray rotating turret
16	Shield ship (shoot to reveal a shield pickup)
19	Asteroid
20	Asteroid, moving faster
26	2x1 turret
27	2x2 turret
34	Formation - Flight of 10, flying in a straight line then splitting up left & right.
35	Formation - Flight of 6 large ships in a diagonal spanning width of the screen.
36	Formation. TODO describe
37	Formation - Two groups flying in from both edges of the screen, then meet in the middle and fly up.
38	Formation - Like 34?
39	Formation - Diagonal of 3 large ships, which split up into 4 smaller ones each.
40	Formation - Diagonal of 3 large ships swaying side-to-side, split up into 4 smaller ones each.
41	Formation - Flight of 10 in from lower left - split up/down around an oval of space, then back together to leave on the right in a line. Seems to be the same for 42 and possibly onwards? There could well be duplicate formations given the sheer number of them.
91	Pickup M
93	Pickup S
94	Pickup R
96	Trigger - End of level
97	Modifier - unknown
116	Single small white ship, flying towards player. Same as the one spawned using ship selector 20 in a formation.
118	Big blue spaceship flying left and right
122-124	Trigger - Adjust flying speed (used in speed levels like E1L2, 122 = normal speed)
133	Trigger - Turns on forward lights (in dark parts of levels)
199	Blue space ship
203	Formation ship selector - 1x1 white space ship (same as 116)
208	Formation ship selector - 1x1 pair of red & blue spheres
238	Prisoner capsule
258	Modifier - Make preceding actor appear only in medium or hard difficulty
259	Modifier - Make preceding actor appear only in hard difficulty

Background actors

Note: background actors have X coordinates greater than 16 in the level files. To make them show up correctly, their X coordinate needs to be adjusted by -16 (the game does that when loading the actors).

ID	Description
10	Stationary green tank
11	???
12	Stationary green tank, animated
13	???
22	Stationary red tank
23	???
24	Stationary red/blue tank/turret
25	???
211	Blue spaceship flying in from below
212	Blue spaceship flying in from above
213	Same as 211 (TODO: Verify there's really no difference)
214	White-blue spaceship flying in from above
223	Red spaceship flying in from below
224	Red spaceship flying in from above
225	Green spaceship flying in from below
226	Green spaceship flying in from above
232	???
237	???

Credits

This file format was reverse engineered by K1n9_Duk3. Lethal_guitar, Primož Vovk, and Timixretroplays are working on figuring out the meaning of the actor IDs. If you find this information helpful in a project you're working on, please give credit where credit is due. (A link back to this wiki would be nice too!)